Insert for freeze-drying apparatus



Sept 22, 1970 y Y H. EILENBERG 3,529,362

INSERT FOR FREEZE-'DRYING APPARATUS Filed March 21, 1968 F/gl 2F 2 lEVACUUM PUMP INVENTOR Hanns Ellenberg ATTORNEYS United States Patent manFiled Mar. 21, 1968, Ser. No. 715,035 Claims priority, applicatitsni(germany, Mar. 21, 1967,

6 Int. c1. Fzsb i3/30, 25/18 U.S. Cl. 34--237 7 Claims ABSTRACT OF THEDISCLOSURE In a container for use in bulk material freeze-dryingapparatus, a supporting means having a wedge-shaped cross section isprovided for supporting the material to be dried. The supporting meansis Water-vapor-permeable and extends along the length of the container,thereby forming a channel for drawing off water vapor from the materialbeing dried. The supporting means is so positioned in the container thatthe narrower end of its wedge-shaped cross section lies along the bottomof the container and the wider end reaches at least to the top of thesurface of the material being dried. By this construction water vaporcan easily and advantageously be extracted from the material beingdried.

BACKGROUND OF THE INVENTION The present invention relates to a containerfor use in freeze-drying apparatus and more particularly for the dryingof bulk materials.

' In containers used for freeze-drying processes, it is important toprovide means for drawing off water vapor from the material being driedso as to facilitate the drying process. Such means have heretofore beenprovided but have proven relatively ineffective, particularly in caseswhere thick layers of material are involved. In such cases, thefreeze-drying operation is made diicult by the lack of sutiicientexposed surface of the material being dried. It is highly desirable tohave as much of the surface of the material being dried exposed aspossible in order to facilitate the drying process. Applicant makes useof this principle by providing means in the freeze-drying containerwhich define channels or vents through the material being dried. By sodoing, drying conditions are greatly enhanced. Moreover, water vaporreleased from the material being dried can more easily be drawn off bymeans of such vents, particularly where fine-grained bulk materials areconcerned. Thus the freeze-drying process as a whole is considerablyimproved.

SUMMARY OF THE INVENTION It is therefore an object of this invention toprovide an improved, relatively simple and yet more effective means forfacilitating the drying of bulk materials in a freezedrying container.

It is also an object of this invention to provide a better means fordrawing water vapor olf from bulk materials being dried in afreeze-drying process.

In brief, the present invention proposes to provide a support meanshaving an element which extends along the length of a container used nfreeze-drying operations. The support means element iswater-vapor-perrneable and serves as a venting element for Water vapordrawn from the drying material. More particularly, the venting elementhas a wedge-shaped cross section and is so disposed in the containerthat the narrower end portion of the wedge-shaped cross section rests onthe bottom of the container and the wider portion of the Wedge-shapedcross section extends vertically at least to the level of the 3,529,362Patented Sept. 22, 1970 ICC upper surface of the material to be dried.By thus positioning the venting member within the material to be dried,openings in the venting element can advantageously be placed at thatlevel where the ice-cotaining core of the material being dried isdisposed during the freezedrying operation. Moreover, the wedge-shapedconfiguration of the venting element advantageously provides a means forreaching water vapors trapped in the upper reaches (with reference tothe bottom or base of the container) of the material being dried. Thesloping sides of the venting element facilitate the collecting of waterfrom the relatively thick material at the bottom of the container. Thus,the venting element, in elfect, provides a means or channel by whichwater vapor is drawn from the material being dried. The angle betweenthe sides of the Wedge-shaped venting member can be relatively narrow sothat the volume, hence the load capacity, of the container is notunnecessarily reduced.

In another form of the present invention, the venting element is a goodheat conductor and is in heat-conducting contact with the bottom and/ orwall surfaces of the container. In addition to drawing water vapor fromthe material being dried, heat can be transferred to the material tofacilitate the drying operation. In such an arrangement, the ventingelement is formed as a perforated or sievelike material with goodheat-conducting property. The use of suitable sintered, screened orsponge-like materials is, however, also possible. The particularmaterial used would depend on the ability of such material to draw offwater vapor extracted from the material being dried equally as well asperforated or sieve-like materials.

In yet another form of the present invention, the venting element isconstructed as a separable element so that it may be removed as a unitfrom the container, as desired. lIt has also been found advantageaus toprovide partitioned portions within the container and a venting elementwithin each portion; venting elements in adjacent partitioned portionsbeing`connected to one another.

BRIIEAF lDESCRIPTION OF THE lDRAWINGS FIG. l is a longitudinal sectionalView taken generally along the plane dened by line 1-1 of FIG. 2,showing a container having a venting element according to the presentinvention.

FIG. 2 is a cross-sectional view of the container taken generally alongthe plane defined by reference line 2 2. of FIG. l and arranged within aschematically shown environmental control device.

FIG. 3 is a schematic and perspective view of the container having aventing member according to the invention as shown in FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring rst to FIG. 1, alongitudinal section of a generally rectangularly shaped container 1 isshown therein. The container 1 includes partition members 3 and, inaddition, venting elements 2. Both members 3 and elements 2 serve assupporting means for any bulk materials introduced into the container 1for freeze-drying. The venting elements 2 include perforations 7, asshown also in FIG. 3, for drawing off water vapor from the materialbeing dried.

Referring now to FIG. 2, as shown therein, the venting elements 2 arecentrally disposed with respect to the space between partition members 3within the container 1. The venting elements 2 are wedge-shaped in crosssection and include a narrow end 4 and a wider end 5. The narrow end 4of the venting element 2 can be formed such that it covers the bottom ofthe container. The container may be arranged in a conventionalenvironmental control device as shown schematically in FIG. 2. Thisdevice basically includes a vacuum chamber having an outlet to a vacuumpump, and a radiant heating element arranged within the chamber.

The venting elements 2 are so arranged that the narrower end 4 of eachelement 2, respectively, is at the bottom of the container 1. The widerend 5 of each venting element 2 is, correspondingly, vertically disposedwith respect to the bottom of the container so that it extends above thetop surface of the material in the container being freeze-dried.

Referred to FIG. 3, the venting elements 2, as shown therein, areconnected to each other by spacers 6. The venting elements 2 areremovably assembled to the container 1. The spacers 6 are used to holdthe venting elements 2 in position when the material to be dried ispoured into container 1. These spacers 6 are located under hocks whichare cut out of the elements 2 in such a manner that the whole ventingassembly is under spring load.

As previously discussed, venting element 2 is watervapor-permeable,being formed of a sieve-like or perforated material. It is alsoconceivable, however, that element 2 can be formed from sintered,screened or sponge-like materials provided such materials, as are used,are as effective as the preferred sieve-like or perforated materials.Another desirable characteristic of the element 2 is that it have goodheat-conducting properties. Venting element 2 is positioned in container1 in good heat-conducting contact with the bottom and/or side Wallsthereof, so that, in addition to drawing water vapor from the materialbeing dried, heat can be transferred to the material during the processto facilitate drying.

It Will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

I claim:

1. In a vessel for freeze-drying apparatus used for drying relativelyfine-grained bulk materials, having provided along an inner surfacethereof a water vapor venting channel, the improvement wherein saidvessel comprises:

(a) a container;

(b) supporting means inserted in said container for supporting thematerials to be dried;

(c) said supporting means having at least one watervapor-permeableventing element;

(d) said venting element having a wedge-shaped cross section andextending along the entire long dimension of the inner surface of saidcontainer;

(e) said venting element having the narrower end of said wedge-shapedcross section in contact with and extending along the bottom of saidcontainer;

(f) the wider end of said wedge-shaped cross section being at least atthe upper surface of such material to be dried, thereby forming achannel in such material to be dried from whence water vapor may beextracted from the material during drying; and

(g) said container being open to the top with said upper wider end ofsaid Wedge-shaped cross section being spaced from other inner surfacesof said container whereby material to be freeze dried may be insertedfrom the top of the container, and water vapor may be vented from saidmaterial to the top of the container as well as through said ventingelement.

2. A vessel as dened in claim 1 wherein said venting element is furtherdefined as being a sieve-like member.

3. A vessel as dened in claim 2 wherein said venting element is formedof a good heat conductor and is in heatconducting contact With thebottom and/or side surfaces of said container.

4. A vessel as defined in claim 3 wherein said venting element isseparably assembled to said vessel in consequence of which said ventingelement is removable therefrom as a structural unit.

5. A vessel as deiined in claim 1 wherein said supporting means furthercomprise:

(a) a plurality of wall members longitudinally extending in said vesseland forming partitioned portions therein;

(b) at least one of said venting elements being disposed in each of saidpartitoned portions; and

(c) means connecting said venting element in adjacent partitionedportions to each other.

6. Apparatus for freeze drying relatively fine-grained bulk materials,having provided along an inner surface thereof a water vapor ventingchannel, the improvement wherein said apparatus comprises:

(a) a container;

(b) supporting means inserted in said container for supporting thematerials to be dried;

(c) said supporting means having at least one Watervapor-permeableventing element;

(d) said venting element having a wedge-shaped cross section andextending along the entire long dimension of the inner surface of saidcontainer;

(e) said venting element having the narrower end of said wedge-shapedcross section in contact with and extending along vthe bottom of saidcontainer;

(f) the wider end of said wedge-shaped cross section being at least atthe upper surface of such material to be dried, thereby forming achannel in such material to be dried from whence vapor may be extractedfrom the material during drying; and

(g) means for subjecting a frozen material within said container to asub-atmospheric pressure and a temperature such that frozen liquidswithin the material are sublimated to a vapor which may be removed viasaid venting element.

7. A method of freezing a relatively fine-grained bulk materialcomprising, in combination:

(a) placing a frozen line-grained material within a container having aventing channel formed along one of its sides, which venting channelincludes a pair of inclined walls which are in contact with the bottomof said container, and which are closely spaced from each other by agreater distance at the top of the container, said walls being vaporpermeable and said venting element being open to the top for the passageof vapor therein,

(b) subjecting the material to a subatmospheric pressure at atemperature at which at least some of the components of said frozenmaterial sublimate to form a vapor, and

(c) withdrawing said vapor through said wedge-shaped channel.

References Cited UNITED STATES PATENTS 1,149,548 8/1915 Rand 34-238 XR1,349,458 8/1920 Johnson 34-238 3,401,468 9/1968 Eilenberg 34-237FOREIGN PATENTS 1,135,831 8/1962 Germany.

FREDERICK L. MATTESON, JR., Primary Examiner H. B. RAMEY, AssistantExaminer

